X-dimethylaminophenyl



Reissued Aug. 17, 1948 3,31-BIS l-DIMETHYLAMINOPHENYL) -6- DIMETHYLAMINOPHTHALIDE Clyde S. Adams, Yellow Springs, Ohio, assignor to The National Cash Register Company, ton, Ohio, a corporation of Maryland No Drawing. Original No. 2,417,897, dated March 25, 1947, Serial No. 599,967,,Iune16,1945: 1 1 plication for reissue November 22, fieoial This invention relates to the new compound 3,3 his(4-dimethylaminophenyl) 5 dimethyl aminophthalide', having the structure N (CH3) 2 and which, for purposes, of convenience, will be referred to herein as the lactone of crystal violet or as crystal violet lactone. ,The'novel compoundhas amelting point of approximately 183 degrees centigrade and crystallifies f'rom' ethyl alcohol in long needle-shaped white crystals.

Thecorripound has-the unique characteristic of;Being'colorlessj'ornearly so, under normal condition's',1'but changes to an intense blue upon being placed in adsorption contact with highly polar substances such" as clay, silicon dioxide, and magnesium carbonate, or when in contact with weak acids. It has, among other utilities, unique value' as an ingredient" of paper-coating compounds which include clay or other dry solid polar-fillers. Such coatings, when suitably made, as:.. describ'ed in the co-pending application of Barrett-Kt Green 'for United States Letters Patent,-Serial TNo. 581,834,.fi1ed March 5, 1945', now abandoned, respond tomarking pressures by produclnga, color. This novel compound, crystal violetlactone, produces a strong color in such coatings, and. isthighly stable against environmental" actionzin both the. polarized and the unpolarizedstates.

, -Qther uses forthe novelsubstance will parallel uses-for other known triphenyl methane lact'ones.

Crystal violet lactone may be prepared by condensing; Michlers hydrol, having the structure 11 with medimethylaminobenzoic acid, having-the structure 1 Claim. (C1. 260 31443) to p oduce a int rmedia p yi 7- biseiifiethyle en b yqrvu dim ii-- m i 'iqbenzoi t i ,twh p si bse il n l x e to ciy'st'al violet l'actone;" 1

Michlers' hydrfolfmay be obtained" commercially; as it is'jan' important intermediatef ihfthe dyestufi industifyybiit L n 'rnethymminohe'nzoicacidis not obtainable even for laboratory use) so an ethod of its'preparation"will'fbe'given:

Preparation" of 'moiynetny mgnmqbengoi oeid' The m-dimethylai ninohenzoic acid 'may The made by the methyliaat'i'o'n of m aifiinatniic acid, having the structure coin using methyl iodide in the presence of anaqueous solution 10f potas hydroxide. The Inaminobenzoic acid is obtainable "comm but at present only'in small amounts?"- It s how ever; a well-known compound.- The 'first" stepin the preparation of n-idimethyla'ininohenzoic acid is'to produce its b'e'tain'. Seventy "grains of m'a'minohe'nz'oic' acidisdissdvedWn 700 flask fitted witha 'cork The resultingini' maybe warmed" to 'efiect completesolu'tionf the solution, when cooled," is added 225'gramsof methyl iodide, followed by"the""addition"of r05 grams of. potassium hydroxide; which-is the approximate strength of the ordinary corfinier cial C..P. product, in'threeseparate harges'of 35 grams each, each ss-gr'amcharge'hein'g "pre viously dissolved, in, cc: of. 50 methyl alcohol. The first cha'rgeis:introduced intb the flask, which is stoppered' and permit'tedtd stand at room temperature until'a-"test'showsthat the" solution is acid. The -second andithirdi charges are added successively, the timi'nlaof' the third charge, as in the case of the second charge,

.The contents v of the flask are now subjected to distillation until most 'oi the methyl alcohol-has e ndi l fi f y reme n n j-aque r m 21 jWW mi ute's, weaned l-l1--' liters of 50% methyl-alcohol, using atwo 4 hydrochloric acid (37% gas content by weight) Condensation of Michlers hydrol with m-dimethis added. On standing and cooling, white crysylaminobenzoic acid tals of the hydrated hydriodic acid salt of m-trimethylbenzbetain separate out. These crystals are filtered on and air dried. 5

The betain, which has the structure The leuco-carboxy compound 2-(4,4'-bisdimethylaminobenzohydryl) -5-dimethylaminobenzoic acid, having the structure 0:0 (OHzhN mom -HI-Hz0 N(OH:): 00:11

is next converted to the methyl ester of m-dimethylaminobenzoic acid in the following man- N 9: ner. Enough of the betain prepared in accordis prepared by condensing Michlers hydrol with ance with the preceding step to make 100 gr m-dimethylaminobenzoic acid, said condensation 1s placed in a wide-mouthed Erlenmeyer flask being represented as f ll w immersed in an oil bath. The temperature is 00 H gradually raised to a point at which the betain (CHWN begins to melt and decompose, giving ofi gaseous HISOI hydrogen iodide and water vapor. The tempera- H 0 OH Mom) ture slowly climbs to a point at which the decom- J position is completed. The decomposition should be carried on slowly and carefully to prevent loss CH N Nam) of product by entrainment. A light oil, which is essentially the free betain, remains in the flask. The temperature of the oil is then raised to 235 degrees centigrade for approximately fifteen H Hi0 minutes, during which the transition of the betain to the corresponding ester takes place. The ester, having the formula more As an example, 18 grams of m-dimethylaminobenzoic acid crystals is mixed and powdered with 27 grams of Michlers hydrol. The resulting in- N(CH3)I timate mixture is then added very slowly to 212 grams of 90% sulphuric acid which has been preis then cooled and solidifies into a wax-like solid. gg ff rfifig gfi gfiig 22 g gz figfifilg stfiggs The ester p e in e Precedmg e 18 during the addition of the mixture. After addith n Sflponlfied 1n the following manner- W' 5 tion of the mixture, the resulting solution is alf ms of the waxy methy ester of lowed to stand at room temperature for several methylaminobenzoic acid is dissolved in a soluhours. The brown acid solution is then poured tion made of 100 milliliters of concentrated hy- Slewly t 1,000 am f ice. The resulting drochlo c d a d 100 {mlhhters of Water- The dilute acid solution is then partially neutralized, result ng solution is boiled for five minutes to While being stirred with a strong sodium hya q y the T acid Solution of droxide solution, followed by more precise neum -d-1methylam1nobenzo1c acid should be treate tralization accomplished by adding sodium carith activated Charcoal a boiled for a few bonate solution as long as the precipitate, which m nutes longer to decolorize it. The resulting fir t forms,redissolves on tirring, Two hundred mixture S fi d Q The TeS1du'a1 a-ctiVated grams of solid hydrated sodium acetate is then charcoa 1 s a hed W a Small qllantlty of hot added, the solution being constantly stirred. The water while still on the filter, and the washings resulting mixture is permitted to stand several are addedtothemainfi ltrate. hours in a cool place. The cooled mixture is Next, fthylammobenzoic acid is isolated filtered to recover the solid condensation prodfrom the resul g acid solution. The acid soluucts, which are washed on the filter with water tion of m-dimethylaminobenzoic acid is cooled and thereafter redissolved in a minimum quanand partially neutralized with a cold saturated tit of dilute hydrochloric acid, plut ion of sod um hydroxide. Final neutraIi a The resulting dilute hydrochloric acid solution tion s accomplished by addl g so carbonate of the condensation products is neutralized with so ut on as lo a the p p w ch fi t a sodium hydroxide solution, excess being added f rm i lv s on sti ri The r s l i g to make the solution definitely alkaline The alsolution is then treated with a saturated solution kaline solution should be boiled for a few minutes o 5011111111 acetate P p d y d s v g 60 gra s cooled, and filtered. The alkaline filtrate con: of hydrated sodium acetate in 50 milliliters of taining the sodium salt of 2-(4,4'-bisdimethyl- Wat he resultmg mixture is allowed to c001,. aminobenzohydryl) -5-dimethy1aminobenz0ic acid and the resulting crystals of m-dimethylaminois acidified with acetic acid, care being taken not benzoic acid are filtered off, washed with a small to add much excess acetic acid after the solution quant ty of cold water, and air dried. This crude becomes acid. The free leuco-carboxy comair-dried product may be further purified by repound-namely, 2-(4,4'-bisdimethylaminobenzocrystallizing it from its solution in hot benzene. hydryl) -5-dimethylaminobenzoic acid --crysta1- lizes out from the acid solution on cooling and standing. This leuco-carboxy compound is filtered OE and dried in a desiccator over a drying substance such as Drierite. The dried leucocarboxy compound is re-crystallized from a hot benzene solution. The resulting gray crystals of 2 (4,4 hisdtmethylaminobenzohydryl) 5 -dimethylarninobenzoic acid, having a melting point of 199-200 degrees centigrade, are filtered off, washed with petroleum ether, and air dried.

Oxidation of the leuco-cwrboxy compound 2-(4.4-bisdimethylaminobenzohydryl) 5 methylaminobeneoic acid One hundred and twelve grams of the dry leuco-carboxy compound is dissolved in 10.7 liters of N/lO hydrochloric acid, and one liter of water is added. Heat may be necessary to complete the solution.

The resulting solution is cooled to zero degrees centigrade by means of an ice-salt bath, and 72 grams of 90% lead dioxide is added slowiv, with stirring, in the form of a thin past-e. The resulting mixture should be stirred for fifteen minutes to complete the oxidation. Forty-two grams of anhydrous sodium sulphate dis-solved in one liter of Water is then added to the oxidation mixture to precipitate the lead as sulphate. The resulting mixture is then treated with sufiicient hydrochloric acid to just dissolve the crystal violet lactone, which tends to precipitate out in the dilute hydrochloric acid during oxidation. The mixture is filtered to remove the lead sulphate, and the filtrate is neutralized with sodium hydroxide solution, making the solution distinctly alkaline. The crystal violet lactone which precipitates out from the alkaline solution is filtered off, washed with a small quantity of cold water, and redissolved in hot 95% ethyl alcohol. If the alcohol solution of the crystal violet lactone ture oHmN N(CH5):

CLYDE S. ADAMS.

REFERENCES CITED The following references are of record in the file of this patent:

I UNITED STATES PATENTS Number Name Date 2,130,430 Austin Sept. 20, 1938 OTHER REFERENCES Chemical Abstracts 32 (1938), page 2106, citing Schwarzengach et al.

Helv. Chem. Acta, 20 (1937), pages 159-1600.

Rec. Trav. Chem., vol. 46, pages 653-98 (page 657) (1927). 

